crystal/step9_try.cr

   1 #! /usr/bin/env crystal run
   2
   3 require "./readline"
   4 require "./reader"
   5 require "./printer"
   6 require "./types"
   7 require "./env"
   8 require "./core"
   9 require "./error"
  10
  11 # Note:
  12 # Employed downcase names because Crystal prohibits uppercase names for methods
  13
  14 module Mal
  15   extend self
  16
  17   def func_of(env, binds, body)
  18     -> (args : Array(Mal::Type)) {
  19       new_env = Mal::Env.new(env, binds, args)
  20       eval(body, new_env)
  21     } as Mal::Func
  22   end
  23
  24   def eval_ast(ast, env)
  25     return ast.map{|n| eval(n, env) as Mal::Type} if ast.is_a? Mal::List
  26
  27     val = ast.unwrap
  28
  29     Mal::Type.new case val
  30     when Mal::Symbol
  31       if e = env.get(val.str)
  32         e
  33       else
  34         eval_error "'#{val.str}' not found"
  35       end
  36     when Mal::List
  37       val.each_with_object(Mal::List.new){|n, l| l << eval(n, env)}
  38     when Mal::Vector
  39       val.each_with_object(Mal::Vector.new){|n, l| l << eval(n, env)}
  40     when Array(Mal::Type)
  41       val.map{|n| eval(n, env)}
  42     when Mal::HashMap
  43       val.each{|k, v| val[k] = eval(v, env)}
  44       val
  45     else
  46       val
  47     end
  48   end
  49
  50   def read(str)
  51     read_str str
  52   end
  53
  54   macro pair?(list)
  55     {{list}}.is_a?(Array) && !{{list}}.empty?
  56   end
  57
  58   def quasiquote(ast)
  59     list = ast.unwrap
  60
  61     unless pair?(list)
  62       return Mal::Type.new(
  63         Mal::List.new << gen_type(Mal::Symbol, "quote") << ast
  64       )
  65     end
  66
  67     head = list.first.unwrap
  68
  69     case
  70     # ("unquote" ...)
  71     when head.is_a?(Mal::Symbol) && head.str == "unquote"
  72       list[1]
  73     # (("splice-unquote" ...) ...)
  74     when pair?(head) && (arg0 = head.first.unwrap).is_a?(Mal::Symbol) && arg0.str == "splice-unquote"
  75       tail = Mal::Type.new list[1..-1].to_mal
  76       Mal::Type.new(
  77         Mal::List.new << gen_type(Mal::Symbol, "concat") << head[1] << quasiquote(tail)
  78       )
  79     else
  80       tail = Mal::Type.new list[1..-1].to_mal
  81       Mal::Type.new(
  82         Mal::List.new << gen_type(Mal::Symbol, "cons") << quasiquote(list.first) << quasiquote(tail)
  83       )
  84     end
  85   end
  86
  87   def macro_call?(ast, env)
  88     list = ast.unwrap
  89     return false unless list.is_a? Mal::List
  90
  91     sym = list.first.unwrap
  92     return false unless sym.is_a? Mal::Symbol
  93
  94     func = env.find(sym.str).try(&.data[sym.str])
  95     return false unless func && func.macro?
  96
  97     true
  98   end
  99
 100   def macroexpand(ast, env)
 101     while macro_call?(ast, env)
 102
 103       # Already checked in macro_call?
 104       list = ast.unwrap as Mal::List
 105       func_sym = list[0].unwrap as Mal::Symbol
 106       func = env.get(func_sym.str).unwrap
 107
 108       case func
 109       when Mal::Func
 110         ast = func.call(list[1..-1])
 111       when Mal::Closure
 112         ast = func.fn.call(list[1..-1])
 113       else
 114         eval_error "macro '#{func_sym.str}' must be function: #{ast}"
 115       end
 116     end
 117
 118     ast
 119   end
 120
 121   macro invoke_list(l, env)
 122     f = eval({{l}}.first, {{env}}).unwrap
 123     args = eval_ast({{l}}[1..-1].to_mal, {{env}})
 124     case f
 125     when Mal::Closure
 126       ast = f.ast
 127       {{env}} = Mal::Env.new(f.env, f.params, args)
 128       next # TCO
 129     when Mal::Func
 130       return f.call args
 131     else
 132       eval_error "expected function as the first argument: #{f}"
 133     end
 134   end
 135
 136   def eval(ast, env)
 137     # 'next' in 'do...end' has a bug in crystal 0.7.1
 138     # https://github.com/manastech/crystal/issues/659
 139     while true
 140       return eval_ast(ast, env) unless ast.unwrap.is_a? Mal::List
 141
 142       ast = macroexpand(ast, env)
 143
 144       list = ast.unwrap
 145
 146       return eval_ast(ast, env) unless list.is_a? Mal::List
 147       return ast if list.empty?
 148
 149       head = list.first.unwrap
 150
 151       return invoke_list(list, env) unless head.is_a? Mal::Symbol
 152
 153       return Mal::Type.new case head.str
 154         when "def!"
 155           eval_error "wrong number of argument for 'def!'" unless list.size == 3
 156           a1 = list[1].unwrap
 157           eval_error "1st argument of 'def!' must be symbol: #{a1}" unless a1.is_a? Mal::Symbol
 158           env.set(a1.str, eval(list[2], env))
 159         when "let*"
 160           eval_error "wrong number of argument for 'def!'" unless list.size == 3
 161
 162           bindings = list[1].unwrap
 163           eval_error "1st argument of 'let*' must be list or vector" unless bindings.is_a? Array
 164           eval_error "size of binding list must be even" unless bindings.size.even?
 165
 166           new_env = Mal::Env.new env
 167           bindings.each_slice(2) do |binding|
 168             key, value = binding
 169             name = key.unwrap
 170             eval_error "name of binding must be specified as symbol #{name}" unless name.is_a? Mal::Symbol
 171             new_env.set(name.str, eval(value, new_env))
 172           end
 173
 174           ast, env = list[2], new_env
 175           next # TCO
 176         when "do"
 177           if list.empty?
 178             ast = Mal::Type.new nil
 179             next
 180           end
 181
 182           eval_ast(list[1..-2].to_mal, env)
 183           ast = list.last
 184           next # TCO
 185         when "if"
 186           ast = unless eval(list[1], env).unwrap
 187             list.size >= 4 ? list[3] : Mal::Type.new(nil)
 188           else
 189             list[2]
 190           end
 191           next # TCO
 192         when "fn*"
 193           params = list[1].unwrap
 194           unless params.is_a? Array
 195             eval_error "'fn*' parameters must be list or vector: #{params}"
 196           end
 197           Mal::Closure.new(list[2], params, env, func_of(env, params, list[2]))
 198         when "quote"
 199           list[1]
 200         when "quasiquote"
 201           ast = quasiquote list[1]
 202           next # TCO
 203         when "defmacro!"
 204           eval_error "wrong number of argument for 'defmacro!'" unless list.size == 3
 205           a1 = list[1].unwrap
 206           eval_error "1st argument of 'defmacro!' must be symbol: #{a1}" unless a1.is_a? Mal::Symbol
 207           env.set(a1.str, eval(list[2], env).tap{|n| n.is_macro = true})
 208         when "macroexpand"
 209           macroexpand(list[1], env)
 210         when "try*"
 211           catch_list = list[2].unwrap
 212           return eval(list[1], env) unless catch_list.is_a? Mal::List
 213
 214           catch_head = catch_list.first.unwrap
 215           return eval(list[1], env) unless catch_head.is_a? Mal::Symbol
 216           return eval(list[1], env) unless catch_head.str == "catch*"
 217
 218           begin
 219             eval(list[1], env)
 220           rescue e : Mal::RuntimeException
 221             new_env = Mal::Env.new(env, [catch_list[1]], [e.thrown])
 222             eval(catch_list[2], new_env)
 223           rescue e
 224             new_env = Mal::Env.new(env, [catch_list[1]], [Mal::Type.new e.message])
 225             eval(catch_list[2], new_env)
 226           end
 227         else
 228           invoke_list(list, env)
 229         end
 230     end
 231   end
 232
 233   def print(result)
 234     pr_str(result, true)
 235   end
 236
 237   def rep(str)
 238     print(eval(read(str), $repl_env))
 239   end
 240 end
 241
 242 $repl_env = Mal::Env.new nil
 243 Mal::NS.each{|k,v| $repl_env.set(k, Mal::Type.new(v))}
 244 $repl_env.set("eval", Mal::Type.new -> (args: Array(Mal::Type)){ Mal.eval(args[0], $repl_env) })
 245 Mal.rep "(def! not (fn* (a) (if a false true)))"
 246 Mal.rep "(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))"
 247 Mal.rep "(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))"
 248 Mal.rep "(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))"
 249
 250 $argv = Mal::List.new
 251 $repl_env.set("*ARGV*", Mal::Type.new $argv)
 252
 253 unless ARGV.empty?
 254   if ARGV.size > 1
 255     ARGV[1..-1].each do |a|
 256       $argv << Mal::Type.new(a)
 257     end
 258   end
 259
 260   begin
 261     Mal.rep "(load-file \"#{ARGV[0]}\")"
 262   rescue e
 263     STDERR.puts e
 264   end
 265   exit
 266 end
 267
 268 while line = my_readline("user> ")
 269   begin
 270     puts Mal.rep(line)
 271   rescue e
 272     STDERR.puts e
 273   end
 274 end